How much do I charge?

How much do the reviewers pay for my item? Amazon might look askance at $0 sales price --- a small amount seems more fair, say $5 for the $18.99 sales price item (MSRP 49.50, Amazon price 39.95, sales price 18.99). Does the reviewer get the item from FBA by purchasing it with a discount code?

Hi Stan,
On Giveaway Service, you give your product for free (or 99% discount) in exchange for an honest review. There have been promotions that business charged $1 or $2 for their product (and then most of them refunded those amounts to authors Paypal address), but it need to be stated in the promotion that authors will be charged for product. Also, authors do not have to pay for shipping. If you do not want to pay shipping you have to emphasize that authors need to have Amazon Prime for free shipping.